The invention relates to an over-center self-closing hinge for cabinet doors, having a quadrilateral linkage, a single-arm lever which is mounted at its one end in the cabinet-wall-related part of the hinge and is constituted by a leaf spring which can flex in a plane at right angles to the hinge axis and thrusts against a cam which is disposed on the inner link (the one closer to the wall) and extends as far as the pivot eye on the link's end nearer the wall, the cam being rotatable on a pivot such that in the end positions of the hinge it comes to rest in two different positions on the inner hinge link.
In one known hinge (U.S. Pat. No. 4,654,930) of this kind, the cam which, in an improvement on an older form (DE-OS 24 08 057), can rotate relative to the inner hinge link, is mounted on a pivot held in the sides of the wall-related hinge part which is an elongated supporting arm of inverted U-shaped cross section Since the cam on the other hand is carried displaceably on the inner hinge link, during the opening or closing movement of the hinge it performs a positively controlled rotatory movement, i e , with each position of the hinge there is positively associated a certain position of the cam body. The swinging movement of the inner hinge link is in this case transmitted to the cam body such that it performs a definitely greater movement relative to the end of the spring biased against it than the cam of the above-mentioned older hinge in which the cam is fixedly joined to the inner hinge link. The positive control of the rotation of the cam makes it possible to increase the effective length of the cam cooperating with the end of the spring, and accordingly also to achieve a relatively greater spring stroke, so that, in comparison to the above-mentioned older hinges, higher end-position retaining forces can be achieved without stronger springs, or equal end-position retaining forces can be achieved with weaker springs. The start of the over-center action, i.e., of the closing torque, when a door mounted on a cabinet carcase with the known hinges approaches the closed position, does not take place abruptly, but gradually, because an abrupt production of the closing torque would require too great a change in the curvature of the cam in the dead-center range, i.e., a portion of the edge of the cam would, in the course of time, be subject to more wear than the other portions. The closing characteristic of the known hinge would therefore also change in the course of time.
It is thus the purpose of the invention to create an over-center self-closing hinge which can turn through most of its range in an effortless and torque-free manner, but at a specific position, just before the closed position is reached, a comparatively strong closing torque spontaneously begins.